Fuel vapour adsorbing device

ABSTRACT

A fuel vapour adsorbing device has a casing having an axis and defining a vapour inlet, a vent connected to the outside environment, and a chamber connected fluidically to the inlet and the vent. The adsorbing device also includes a filter material housed in the chamber; a cover wall covering the chamber; and an elastic mechanism and, preferably, a grille, which are integral with the cover wall and cooperate with the filter material.

TECHNICAL FIELD

The present invention relates to a fuel vapour adsorbing device, orcanister, for a motor vehicle tank.

BACKGROUND ART

Canisters are known comprising a casing defining a chamber; and a filterhoused inside the chamber and comprising bulk granules of adsorbentmaterial, such as active carbon. More specifically, the casing definesan inlet for fuel vapour from the tank; an outlet communicating with theoutside environment; and a hatch connected to the intake manifold of aninternal combustion engine of the vehicle to perform cleaning cycles ofthe active carbon.

An active-carbon canister normally also comprises a grille cooperatingwith the active carbon; and elastic means interposed between a cover ofthe canister and the grille to compact the active carbon and prevent thegranules from being damaged by stress during normal use of the vehicle,e.g. by jolting when running along uneven roads.

An adsorbing device according to the preamble of claim 1 is disclosed inU.S. Pat. No. 4,693,393.

Assembling the cover, the elastic means, and the grille, however,involve a relatively large number of operations, which increasemanufacturing time.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a canister designedto eliminate the above drawback.

According to the present invention, there is provided a canister asclaimed in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will be described by wayof example with reference to the accompanying drawings, in which:

FIG. 1 shows a longitudinal section of a canister in accordance with thepresent invention;

FIG. 2 shows a section of a preferred embodiment of a detail in FIG. 1;

FIG. 3 shows a view in perspective of a cover of the FIG. 1 canister.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in FIG. 1 indicates as a whole a canister comprising a casing 2defining a chamber 3; and a cover 4 connected to casing 2 to closechamber 3.

More specifically, casing 2 is truncated-cone-shaped, and comprises,integrally, a bottom wall 5, a lateral wall 6 axially symmetrical withrespect to an axis A, and two tubular projections 7 and 8 projectingfrom bottom wall 5 on the opposite side of bottom wall 5 to lateral wall6.

Tubular projections 7 and 8 respectively define an inlet 7 and an outlet8 connecting chamber 3 fluidically to a fuel tank (not shown) and to anintake manifold (not shown) of an internal combustion enginerespectively.

Canister 1 also comprises a diffuser 9 connected fluidically to theinlet and housed inside chamber 3.

Diffuser 9 is tubular, and defines a number of openings 10 located at apredetermined axial height to diffuse the gas mixture inside chamber 3.

Canister 1 also comprises a first felt 11 resting on bottom wall 5; anadsorbent material 12, e.g. granular active carbon, housed in chamber 3,on top of felt 11; and a second felt 13 interposed between adsorbentmaterial 12 and cover 4.

FIG. 2 shows an end portion 14 of casing 2 in accordance with apreferred embodiment. More specifically, end portion 14 is located atthe opposite axial end to bottom wall 5, and defines a labyrinth seal.

The labyrinth seal preferably comprises an end portion 15 of lateralwall 6; an annular member 16 surrounding end portion 15; and a coverwall 17 of cover 4.

More specifically, annular member 16 comprises, integrally, acylindrical wall 18 coaxial with axis A and larger in diameter than endportion 15; and a sloping wall 19 converging with and forming one piecewith lateral wall 6.

Sloping wall 19 defines, together with end portion 15, a number ofpassages 20; and cylindrical wall 18 defines a number of openings 21cooperating with respective radial projections 22 on cover 4 to define aclick-on fastener.

When cover 4 is positioned closing casing 2, a gap 23 is convenientlydefined by end portion 15, annular member 16, and cover wall 17.

When cover 4 is in the closed position, gap 23 communicates fluidicallywith the outside environment through passages 20, and with chamber 3through a relief passage 24 defined between end portion 15 and coverwall 17 and located axially higher than passages 20.

Moreover, each opening 21 is axially larger than relative radialprojection 22 to define a passage 25 connecting gap 23 to the outsideenvironment.

Casing 2 is preferably made of polymer material and molded in one piece.

FIG. 3 shows cover 4, which comprises, integrally, cover wall 17; radialprojections 22 on cover wall 17; a grille 26 cooperating with felt 13;and two elastic members 27 interposed between cover wall 17 and grille26 to compact adsorbent material 12 when cover 4 is closed.

More specifically, elastic members 27 are axially symmetrical withrespect to axis A, and each comprise a straight, substantially S-shapedwall (FIG. 2) having end portions connected to cover wall 17 and grille26 respectively.

Cover wall 17 preferably has a face 28 facing grille 26 and defining anannular wall 29 and a cylindrical projection 30 concentric with annularwall 29.

More specifically, annular wall 29 has an inside diameter larger thanthe outside diameter of end portion 15, and defines, with cylindricalprojection 30, a groove 31 housing end portion 15 both axially andradially loosely to define passage 24 when cover 4 is closed onto casing2.

When assembling canister 1, felt 11 is placed on bottom wall 5, and theactive carbon is deposited on felt 11 to prevent it escaping fromtubular projections 7 and 8.

Felt 13 is then applied, and cover 4 is closed onto casing 2 by theclick-on fastener defined by radial projections 22 and openings 21. Inthe closed position, cover 4 is maintained at such an axial height thatelastic members 27 are compressed and exert, by means of grille 26 andfelt 13, substantially uniform pressure to compact the active carbon.

Cover 4 and, in particular, cover wall 17, elastic members 27, andgrille 26 are preferably made of polymer material and molded in onepiece.

Canister 1 operates as follows.

An air-vapour mixture from the vehicle tank flows into chamber 3 throughtubular projection 7 and openings 10 in diffuser 9, at a roughlyintermediate height with respect to the active-carbon level insidecasing 2.

Active carbon 12 retains the fuel vapour and allows the air, containingno fuel vapour, to flow out through felt 13, grille 26, and passage 24into the outside environment.

More specifically, felt 13 retains the active carbon inside chamber 3,and prevents particles from escaping through passage 24 into the outsideenvironment.

During the cleaning cycle, the vacuum created by the intake manifold andthe force of gravity draw outside air through passage 24 and force thefuel vapour to the outlet defined by tubular projection 8.

The air flowing in through passage 24 during the cleaning cycle maycontain particles of water or impurities. In which case, the particlesflow into gap 23 through passage 25, but, being heavier than air, flowout by gravity through passages 20, whereas the air, containingsubstantially no particles, flows up to passage 24 and eventually intochamber 3.

The advantages of canister 1 according to the present invention are asfollows.

Elastic members 27 formed integrally with cover 4 eliminate severalassembly operations, and reduce both manufacturing time and the numberof component parts of canister 1.

Click-on connection of cover 4 to casing 2 eliminates the need for laseror vibration welding and the high-cost equipment involved, and alsofurther reduces assembly time by eliminating the testing operationrequired by laser or vibration welded covers.

The labyrinth seal defined at end portion 14 is an effective, compactbarrier preventing water particles from entering canister 1.

More specifically, the fact that passage 24 is defined between cover 4and end portion 15 of lateral wall 6, that projections 22 directlyengage annular member 16, and that passages 25 are defined by openings21, are all design solutions which simplify the geometry of thecomponent parts and assembly, and avoid back drafts in the molds.

The above are also achieved by virtue of passage 24 being definedbetween cover 4 and casing 2.

Clearly, changes may be made to canister 1 as described and illustratedherein without, however, departing from the scope of the presentinvention as defined in the accompanying Claims.

Canister 1 need not have the labyrinth seal shown in FIG. 2. In thissimplified embodiment (FIG. 1), cover 4 clicks onto a flange 32 integralwith end portion 15 of lateral wall 6, and passage 24 is defined betweenflange 32 and cover wall 17.

Felt 13 may be glued to grille 26 to further simplify assembly.

Grille 26 may be separate from elastic members 27, and only cover wall17 and elastic members 27 may be formed in one piece.

1) A fuel vapour adsorbing device (1) comprising a casing (2) having anaxis (A) and defining a vapour inlet (7), a vent (24) connected to theoutside environment, an outlet (8), and a chamber (3) connectedfluidically to said inlet, said outlet, and said vent (7, 8, 24); saidadsorbing device (1) also comprising a filter material (12) housed insaid chamber (3); a cover wall (17) covering said chamber (3); and anelastic mechanism (27) cooperating with said filter material (12) andbeing integral with said cover wall (17) and configured to compact saidfilter material (12). 2) The adsorbing device (1) as claimed in claim 1,wherein said vent (24) is defined between said casing (2) and said coverwall (17). 3) The adsorbing device (1) as claimed in claim 2, furtherincluding a labyrinth seal (15, 17, 19) connected fluidically to saidvent (24). 4) The adsorbing device (1) as claimed in claim 3, whereinsaid labyrinth seal comprises an axial end portion (15) of said casing(2), and an annular member (16) of said casing (2) defining a gap (23)with said end portion (15); said gap (23) being connected fluidicallywith the outside environment, with said vent (24), and with at least oneaperture (20) located at an axial height lower than that of said vent(24). 5) The adsorbing device (1) as claimed in claim 1, furtherincluding click-on connector (21, 22) interposed between said cover wall(17) and said casing (2). 6) The adsorbing device (1) as claimed inclaim 3, wherein said cover wall (17) defines a portion of saidlabyrinth seal. 7) The adsorbing device (1) as claimed in claim 6,wherein said cover wall (17) defines an annular groove (31) housing saidend portion (15) both axially and radially loosely to define said vent(24). 8) The adsorbing device (1) as claimed in claim 4, wherein saidclick-on connecting means (21, 22) comprise a number of projections (22)on said cover wall (17), and a corresponding number of openings (21)defined by said annular member (16). 9) The adsorbing device (1) asclaimed in claim 8, wherein said openings (21) are sized to define apassage (25) connecting said gap (23) to the outside environment whensaid projections (22) engage the openings (21) and when said cover wall(17) is connected to said casing (2). 10) The adsorbing device (1) asclaimed in claim 4, wherein said annular member (16) is formed in onepiece with said end portion (15) and is molded. 11) The adsorbing device(1) as claimed in claim 1, further including a grille (26) integrallyformed with said elastic mechanism (27).